System and method for dry fracture shale energy extraction

ABSTRACT

A system and method are provided that use RF energy to enhance the extraction of oil and gas from hydrocarbon bearing strata. A three-dimensional underground electromagnetic array is used to guide RF energy to where that energy is converted to heat in the hydrocarbon bearing strata. The three dimensional underground electromagnetic array is a guided wave structure, as opposed to an antenna structure, to minimize the unwanted effects of the near fields associated with antennas. In one embodiment, the legs of the three-dimensional underground electromagnetic array are composed of production well pipe.

The present application claims priority from: U.S. ProvisionalApplication No. 62/037,145, filed Aug. 14, 2014; U.S. ProvisionalApplication No. 62/037,147, filed Aug. 14, 2014; U.S. ProvisionalApplication No. 62/037,148, filed Aug. 14, 2014; U.S. ProvisionalApplication No. 62/037,151, filed Aug. 14, 2014; U.S. ProvisionalApplication No. 62/037,154, filed Aug. 14, 2014; U.S. ProvisionalApplication No. 62/037,156, filed Aug. 14, 2014; and U.S. ProvisionalApplication No. 62/037,159, filed Aug. 14, 2014, the entire disclosuresof which are incorporated herein by reference.

BACKGROUND

The present invention generally deals with systems and methods for theenhanced extraction of oil and gas from hydrocarbon bearing strata usingRF heating to cause increased permeability and in situ pyrolysis.

Extraction of oil from oil shale, or more generally, hydrocarbon bearingstrata, is an industrial process for oil production. This processconverts kerogen in hydrocarbon bearing strata into oil by pyrolysis,hydrogenation, or thermal dissolution. The resultant oil is used as fueloil or upgraded to meet refinery feedstock specifications by addinghydrogen and removing sulfur and nitrogen impurities. Kerogen isconsidered to have been formed by the deposition of plant and animalremains in marine and non-marine environments. Each kerogen deposit isunique. Alteration of this deposited material during subsequentgeological periods produced a wide variety of kerogen maturities. Sourcematerial and conditions of deposition are the major factors influencingthe type of kerogen and hence the amount and quality of oil and/or gasformed.

Extraction of oil from hydrocarbon bearing strata in the past has beenperformed above ground (ex situ processing) by mining the hydrocarbonbearing strata and then treating it in processing facilities. Newermodern technologies are being used to attempt the processing underground(in situ processing) by applying heat and extracting the oil via oilwells. The quality of the oils from shale are highly dependent on thetemperature at which the kerogen is “cooked” either in situ or aboveground and generally consists of variable molecular weight organicliquids, gasses and condensates.

In situ technologies heat hydrocarbon bearing strata underground byinjecting hot fluids into the rock formation, or by using linear orplanar heating sources followed by thermal conduction and convection todistribute heat through the target area. The oil is then recoveredthrough vertical wells drilled into the formation. These technologiesare potentially able to extract more oil from a given area of land thanconventional ex situ processing technologies, as the wells can reachgreater depths than surface mines. Unlike for underground mining, thereis no requirement to leave pillars in place to prevent roof collapse,which also equates to more oil and gas from the same volume. They alsopresent an opportunity to recover oil from low-grade deposits wheretraditional mining techniques would be uneconomical.

An in situ shale retort can be formed by many methods, such as themethods disclosed in U.S. Pat. No. 4,043,598 to Gordon B. French et al.The process can also be practiced on shale oil produced by other methodsof retorting. Many of these methods for shale oil production aredescribed in Synthetic Fuels Data Handbook, compiled by Dr. Thomas A.Henrickson, and published by Cameron Engineers. Inc., Denver, Colo. Forexample, other processes for retorting hydrocarbon bearing stratainclude those known as the TOSCO, Paraho Direct, Paraho Indirect, N-T-U,and Bureau of Mines, Rock Springs, processes.

The Illinois Institute of Technology developed the concept ofhydrocarbon bearing strata volumetric heating using radio waves (radiofrequency processing) during the late 1970s. This technology was furtherdeveloped by Lawrence Livermore National Laboratory. Hydrocarbon bearingstrata is heated by vertical electrode arrays. Deeper volumes could beprocessed at slower heating rates by installations spaced at tens ofmeters. The concept presumes a radio frequency at which the skin depthis many tens of meters, thereby overcoming the thermal diffusion timesneeded for conductive heating. Its drawbacks include intensiveelectrical demand and the possibility that groundwater or char wouldabsorb undue amounts of the energy.

Microwave heating technologies are based on the same principles as radiowave heating, although it is believed that radio wave heating is animprovement over microwave heating because its energy can penetratefarther into the hydrocarbon bearing strata. The microwave heatingprocess was tested by Global Resource Corporation. Electro-Petroleumproposes electrically enhanced oil recovery by the passage of directcurrent between cathodes in producing wells and anodes located either atthe surface or at depth in other wells. The passage of the currentthrough the hydrocarbon bearing strata results in resistive Jouleheating.

In many cases, before an in situ retorting process can function, it isnecessary to develop techniques to increase the permeability of thehydrocarbon bearing strata. Induced fracturing, the best method ofincreasing the effective permeability of oil-shale deposits, may beaccomplished by hydraulic pressure, high explosives, high-voltageelectricity, or heating of the formation, or combinations of two or moreof these.

Hydraulic fracturing, or fracking, has played an important role in thedevelopment of America's oil and natural gas resources for nearly 60years. In the U.S., an estimated 35,000 wells are processed with thehydraulic fracturing method; it's estimated that over one million wellshave been hydraulically fractured since the first well in the late1940s. Each well is a little different, and each one offers lessonslearned. The oil and natural gas production industry uses these lessonsto develop best practices to minimize the environmental and societalimpacts associated with development. Studies estimate that up to 80percent of natural gas wells drilled in the next decade will requirehydraulic fracturing to properly complete well setup. Horizontaldrilling is a key component in the hydraulic fracturing process.

In a hydraulic fracturing job, “fracturing fluids” or “pumping fluids”consisting primarily of water and sand are injected under high pressureinto the producing formation, creating fissures that allow resources tomove freely from rock pores where it is trapped. Typically, steel pipeknown as surface casing is cemented into place at the uppermost portionof a well for the explicit purpose of protecting the groundwater. Thedepth of the surface casing is generally determined based on groundwaterprotection, among other factors. As the well is drilled deeper,additional casing is installed to isolate the formation(s) from whichoil or natural gas is to be produced, which further protects groundwaterfrom the producing formations in the well. Casing and cementing arecritical parts of the well construction that not only protect any waterzones, but are also important to successful oil or natural gasproduction from hydrocarbon bearing zones. Industry well designpractices protect sources of drinking water from the other geologic zoneof an oil and natural gas well with multiple layers of impervious rock.While 99.5 percent of the fluids used consist of water and sand, somechemicals are added to improve the flow. The composition of the chemicalmixes varies from well to well.

Hydraulic fracturing has been successful at increasing the flow of gasfrom low permeability shales. Low permeability shales are those in whichthe permeability is than 1 microdarcy and oil and gas cannot berecovered economically without well stimulation. This wet fracturing hasbeen shown to increase the amount of flow from a well many times over bycausing cracks in the shale to expose large areas of gas to harvesting.One issue with hydraulic fracturing is that it requires the use of largeamounts water at high pressure to cause fractures in the undergroundhydrocarbon bearing shale. This water is mixed with various chemicals,an individual proprietary mixture for each fracking company, to helpwith the fracturing process. The amount of water used per well varies bylocation but can be as much as 4 to 5 million gallons. Getting this muchwater to the well head can cause wear problems for local roads due tothe 400 to 500 heavy tanker trucks required. Pumping this water cancause significant level reduction in local aquifers, which can causelocal water wells to run dry. In addition, 10% to 40% of this watercomes back to the surface contaminated with subsurface chemicals andneeds to be cleaned up before release into the environment, or disposedof in some other environmentally responsible manner. The amount of waterrequired to open up hydrocarbon seal shales has been called the singlebiggest problem in the shale gas industry

What is needed is a system and method, which can recover the oil and gasin place from subsurface low permeability hydrocarbon bearing stratawith minimal water usage. Further, the system and method should also becapable of converting the kerogen within the hydrocarbon bearing stratainto additional oil and gas, which can also recovered.

SUMMARY

The present invention is drawn to a system and method for recovering theoil and gas in place from subsurface low permeability hydrocarbonbearing strata with minimal water usage. Further, the system and methodis capable of converting the kerogen within the hydrocarbon bearingstrata into additional oil and gas, which can also recovered.

An aspect of the present invention is drawn to system including a firstprimary-phase well pipe segment, a primary-phase dielectric spacer, asecond primary-phase well pipe segment, a first RF transmission line, afirst RF coupler, a first secondary-phase well pipe segment, asecondary-phase dielectric spacer, a second secondary-phase well pipesegment, a second RF transmission line and a second RF coupler. Theprimary-phase dielectric spacer is connected to the first primary-phasewell pipe segment. The second primary-phase well pipe segment isconnected to the primary-phase dielectric spacer such that theprimary-phase dielectric spacer is disposed between the firstprimary-phase well pipe segment and the second primary-phase well pipesegment. The first RF transmission line can be disposed into the firstprimary-phase well pipe segment and into the second primary-phase wellpipe segment and can transmit a first RF signal. The first RF couplercan be disposed within one of the first primary-phase well pipe segmentsand the second primary-phase well pipe segment, can couple the first RFsignal from the first RF transmission line to the first primary-phasewell pipe segment when disposed within the first primary-phase well pipesegment, and can couple the first RF signal from the first RFtransmission line to the second primary-phase well pipe segment whendisposed within the second primary-phase well pipe segment. Thesecondary-phase dielectric spacer is connected to the firstsecondary-phase well pipe segment. The second secondary-phase well pipesegment is connected to the secondary-phase dielectric spacer such thatthe secondary-phase dielectric spacer is disposed between the firstsecondary-phase well pipe segment and the second secondary-phase wellpipe segment. The second RF transmission line can be disposed into thefirst secondary-phase well pipe segment and into the secondsecondary-phase well pipe segment and can transmit a second RF signal.The second RF coupler can be disposed within one of the firstsecondary-phase well pipe segment and the second secondary-phase wellpipe segment, can couple the second RF signal from the second RFtransmission line to the first secondary-phase well pipe segment whendisposed within the first secondary-phase well pipe segment, and cancouple the second RF signal from the second RF transmission line to thesecond secondary-phase well pipe segment when disposed within the secondsecondary-phase well pipe segment. The first primary-phase well pipesegment and the first secondary-phase well pipe segment form a two-wiretransmission line when the first RF coupler is disposed within the firstprimary-phase well pipe segment and when the second RF coupler isdisposed within the second primary-phase well pipe segment.

BRIEF SUMMARY OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate an exemplary embodiment of the presentinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings:

FIG. 1 illustrates an example dry fracture shale energy extractionsystem in accordance with aspects of the present invention;

FIG. 2 illustrates a portion of the vertical well pipe and well pipes ofFIG. 1 between double arrows AA and BB;

FIG. 3a illustrates a position of a primary-phase RF transparent wellpipe coupler within a primary-phase RF transparent well pipe at time t₁;

FIG. 3b illustrates a position of the primary-phase RF transparent wellpipe coupler within the primary-phase RF transparent well pipe at timet₂;

FIG. 4 illustrates a primary-phase RF transparent well pipe, asecondary-phase RF transparent well pipe, and a heating zone around theprimary-phase RF transparent well pipe coupler and a secondary-phase RFtransparent well pipe coupler at time t₁;

FIG. 5a illustrates a primary-phase RF coupler placement within aprimary-phase segmented well pipe at time t₃, in accordance with aspectsof the present invention;

FIG. 5b illustrates another location for the primary-phase RF couplerplacement within primary-phase segmented well pipe at time t₄, inaccordance with aspects of the present invention;

FIG. 6 illustrates a primary-phase segmented well pipe section betweendouble arrows CC and DD of FIG. 1, in accordance with aspects of thepresent invention;

FIG. 7 illustrates both primary-phase segmented well pipe section 600and secondary-phase segmented well pipe section 700 between doublearrows CC and DD of FIG. 1, in accordance with aspects of the presentinvention;

FIG. 8a illustrates a two-wire transmission line having a primary-phasewell pipe and a secondary-phase well pipe, in accordance with aspects ofthe present invention;

FIG. 8b illustrates a four-wire transmission line formed from wellpipes, in accordance with aspects of the present invention;

FIG. 8e illustrates a rectangular, six-wire transmission line formedfrom well pipes, in accordance with aspects of the present invention;

FIG. 8d illustrates a square, nine-wire transmission line formed fromwell pipes, in accordance with aspects of the present invention;

FIG. 8e illustrates a five-wire transmission line formed from wellpipes, in accordance with aspects of the present invention;

FIG. 9 illustrates an example direct connection RF coupler, inaccordance with aspects of the present invention;

FIG. 10 illustrates an example inductive RF coupler, in accordance withaspects of the present invention;

FIG. 11 illustrates an inductive RF coupler connected to a conductivesegment of a primary-phase segmented well pipe, in accordance withaspects of the present invention;

FIG. 12 illustrates an inductive coupler connected to two conductivesegments of a primary-phase segmented well pipe, in accordance withaspects of the present invention;

FIG. 13 illustrates an example capacitive RF coupler, in accordance withaspects of the present invention;

FIG. 14 illustrates an example hydrocarbon lock to feed the RF powerdown into the well without loss of oil or gas to the environment, inaccordance with aspects of the present invention;

FIG. 15 illustrates an example sensor suite, which will regulate andoptimize the functioning of a dry fracture shale energy extractionsystem, in accordance with aspects of the present invention; and

FIG. 16 illustrates heating patterns for a square, three-dimensionalunderground electromagnetic array realization of a dry fracture shaleenergy extraction system, for heating specific sections of hydrocarbonbearing strata by controlling which well pipe segments containprimary-phase RF signals and which contain secondary-phase of two RFsignals, in accordance with aspects of the present invention.

DETAILED DESCRIPTION

The system and method described herein concerns the use of RF energy toenhance the extraction of oil and gas from hydrocarbon bearing strata.It uses a three-dimensional underground electromagnetic array to guideRF energy to where that energy is converted to heat in the hydrocarbonbearing strata. The three dimensional underground electromagnetic arrayis a guided wave structure, as opposed to an antenna structure, tominimize the unwanted effects of the near fields associated withantennas. In one realization, the legs of the three-dimensionalunderground electromagnetic array are composed of production well pipe.

The system and method are designed to work along the entire extent of ahorizontally drilled well bore such as are used to efficiently extractoil and gas from hydrocarbon bearing strata with large horizontal extendand smaller vertical extent. There are multiple three dimensionalunderground electromagnetic arrays along the length of the well boreallowing the heating of individual volumes of rock (e.g. 100,000 tons,50,000 cubic yards).

The heat deposited in the hydrocarbon bearing strata has two effects.First it causes stresses in the hydrocarbon strata that will causecracking and hence will increase the permeability of the strata. Thesestresses are caused by thermal gradients and by differential thermalexpansion. The stress required to cause cracking may also be reduced bychemical changes in the hydrocarbon strata, which reduce the strength ofthe rock. Second the heating will cause in situ pyrolysis of the kerogenin the strata releasing additional oil and gas to be recovered.

The release of the additional oil and gas combined with additional wellpipes required to form the three dimensional underground electromagneticarrays means that more oil and gas per volume will be recovered thanthrough any other method of enhanced oil and gas production. Further thesystem and method herein will not require the large amount of water thatis currently used in hydraulic fracturing.

The present invention is drawn to a system and method for recovering theoil and gas in place from subsurface low permeability hydrocarbonbearing strata with minimal water usage. Further the system and methodwill be capable of converting the kerogen within the hydrocarbon bearingstrata into additional oil and gas, which can also recovered

Aspects of the present invention will now be described with reference toFIGS. 1-16.

The main aspects of the present invention, are described with referenceto FIGS. 1 and 2 and are applicable to all embodiments of the invention.The first embodiment of the present invention is described withreference to FIGS. 3a, 3b and 4. The second embodiment of the inventionis described with references to FIGS. 5a, 5a , 6 and 7 and FIGS. 9-13.Additional aspects of the system, which apply to both embodiments, aredescribed with reference to FIG. 8 and FIGS. 14-16.

The main aspects of the present invention are now described withreference to FIGS. 1 and 2.

FIG. 1 illustrates an example dry fracture shale energy extractionsystem 100 in accordance with aspects of the present invention.

As shown in the figure, dry fracture shale energy extraction system 100includes a Radio Frequency (RF) generator 102, a primary-phase centerconductor RF transmission line 104, a secondary-phase center conductorRF transmission line 106, a hydrocarbon lock 108, a primary-phase wellpipe 110, and a secondary-phase well pipe 112. Additionally shown in thefigure are a vertical well pipe 114, an oil recovery pipe 116, an oilstorage tank 118, an RF heating zone 120 around first andsecondary-phase well pipes 110 and 112, a surface of the earth 122, arock overburden 124, hydrocarbon bearing strata 126, an upper boundary128 to hydrocarbon bearing strata 126, and a lower boundary 130 tohydrocarbon bearing strata 126.

RF generator 102 is located above ground and is electrically connectedto first and secondary-phase center conductor RF transmission lines 104and 106. Primary-phase center conductor RF transmission line 104 andsecondary-phase center conductor RF transmission line 106 are directedinto vertical well pipe section 114 through hydrocarbon lock 108 andthey run down the inside of vertical well pipe section 114.Primary-phase center conductor RF transmission line 104 continues insideof primary-phase well pipe 110. Secondary-phase center conductor RFtransmission line 106 continues inside of secondary-phase well pipe 112.Primary-phase well pipe 110 is electrically coupled to secondary-phasewell pipe 112. Primary-phase well pipe 110 parallel or nearly parallelto secondary-phase well pipe 112 in RF heating zone 120. Oil, producedin RF heating zone 120, flows through primary-phase well pipe 110 andsecondary-phase well pipe 112 then up vertical well pipe 114.Hydrocarbon lock 108 is connected to vertical well pipe 114 and to oilrecovery pipe 116. Oil recovery pipe 116 is connected to oil storagetank 118. RF generator 102, hydrocarbon lock 108, oil recovery pipe 116,oil storage tank 118, part of primary-phase center conductor RFtransmission line 104, and part of secondary-phase center conductor RFtransmission line 106 are located above surface of the earth 122.Hydrocarbon bearing strata 126 is located under overburden 124 andcontains kerogen. Heating zone 120, located within hydrocarbon bearingstrata 126 also contains oil and gas from the heating process.

RF generator 102 may be any device or system, which produces the RFsignals sufficiently high in power to convert the kerogen in hydrocarbonbearing strata 126 to oil and gas within a predetermined time frame,e.g. a year. The frequency of an RF signal provided by RF generator 102is set to optimize heating hydrocarbon bearing strata 126 and tominimize loss in primary-phase center conductor RF transmission line 104and secondary-phase center conductor RF transmission line 106.Non-limiting examples of a frequency of an RF signal provided by RFgenerator 102 include those between 100 KHZ and 30 MHz. A duty cycle ofthe waveform of an RF signal provided by RF generator 102 may be between10% and 100% depending on system optimization. Non-limiting examples ofRF generator 102 include large vacuum tube systems or solid statesystems.

Primary-phase center conductor RF transmission line 104 may be anydevice or system, which is a conduit for carrying the primary-phase highpower RF signal. Secondary-phase center conductor RF transmission line106 may be any device or system, which is a conduit for carrying thesecondary-phase RF signal. Primary-phase center conductor RFtransmission line 104 and secondary-phase center conductor RFtransmission line 106 are small enough to fit within a standard 4.7 inchinner diameter well pipe and still allow sufficient space for the flowof oil and gas back up primary-phase well pipe 110 and secondary-phasewell pipe 112. Primary-phase center conductor RF transmission line 104and secondary-phase center conductor RF transmission line 106 are strongenough to withstand the vertical pipe runs and able to function in theunderground temperature and pressure environment. Signal loss may beheld, for example, to lower than 3 db per 5000 ft. Non-limiting examplesof transmission lines include coaxial, twin lead, and shielded twinlead. For purposes of clarity 104 and 106 will be called first andsecondary-phase center conductor RF transmission lines, respectively, inthis disclosure.

Hydrocarbon lock 108 may be any device or system, which forms a sealthrough which center conductor RF transmission lines 104 and 106 areinserted into or retracted from vertical well pipe 114 without lettingoil or gas escape. Hydrocarbon lock 108 also guides the oil into oilrecovery pipe 116. Hydrocarbon lock 108 withstands and functionsproperly in the presence of oil and gas that have been heated to hightemperature in RF heating zone 120. Hydrocarbon lock 108 will bedescribed in more detail below.

In conventional oil well construction, a metal well pipe may be used inthe oil producing section depending on the ability of the rock towithstand collapse. Primary-phase well pipe 110 may be any device orsystem, which provides structure to keep a well hole from collapsingduring heating. Primary-phase well pipe 110 can be either RF transparentor segmented with alternating conductive pipes and dielectric spacers.Secondary-phase well pipe 112 may be any device or system, whichprovides structure to keep the well hole from collapsing during heating.Secondary-phase well pipe 112 can be either RF transparent or segmentedwith alternating conductive pipes and dielectric spacers. Vertical wellpipe 114 may be any device or system, which forms the vertical sectionof the well. Vertical well pipe 114, primary-phase well pipe 110 andsecondary-phase well pipe 112 are all conduits for center conductor RFtransmission lines 104 and 106, and oil.

Oil recovery pipe 116 may be any device or system, which guides oil. Oilstorage tank 118 may be any device or system, which stores oil. RFheating zone 120 heats hydrocarbon bearing strata 126 and covertskerogen to oil and gas.

In operation, dry fracture shale energy extraction system 100 enhancesoil and gas recovery from hydrocarbon bearing strata 126, utilizing anarchitecture of electromagnetic field heating, sensors and controls toheat large blocks of hydrocarbon bearing strata 126 to over 300° C.,causing cracking of hydrocarbon bearing strata 126 and in situ retortingof the kerogen.

Electromagnetic energy is used to deposit heat into hydrocarbon bearingstrata 126. The interaction is between the electric field and theimaginary part of the permittivity, which is the dielectric analogue tojoule resistance heating (ohmic loss) in a non-perfect conductor. Therelationship between power deposited and the electric field is given by:P=2π∈″E ²,which is discussed in Engineers' Handbook of Industrial MicrowaveHeating, by Roger J. Meredith, and wherein P is the power per unitvolume, f is the frequency, ∈″ is the complex permittivity of thematerial, and E is the electric field strength. The applied E fielddeposits energy into hydrocarbon bearing strata 126, which causes atemperature increase leading to stress, cracking, and pyrolysis of thekerogen in hydrocarbon bearing strata 126. The stress/cracking is causedboth by the expansion of hydrocarbon bearing strata 126 and theexpansion of the water trapped within hydrocarbon bearing strata 126.The value “∈” comes from a combination of water, rock, and kerogenwithin hydrocarbon bearing strata 126 with water being the biggestcontributor. As the water superheats and boils off, the overallpermittivity will change.

Dry fracture shale energy extraction system 100 includes sets ofthree-dimensional underground electromagnetic arrays. FIG. 1 shows oneexample of a three-dimensional underground electromagnetic array formedfrom primary-phase well pipe 110 and secondary-phase well pipe 112. Thisforms a 2 row by 1 column three-dimensional underground electromagneticarray. The three-dimensional underground electromagnetic arrays are notlimited to be 2 rows 1 by column. They can be n by m, where n is thenumber of rows and m is the number of columns. More example variationsof the three-dimensional underground electromagnetic array are shownlater in the disclosure.

These three-dimensional underground electromagnetic arrays are used toguide the electromagnetic fields and control their intensity over largeblocks (e.g. 100,000 tons, 50,000 yds³) of hydrocarbon bearing strata126. The underground three-dimensional electromagnetic arrays includegroups of multi-wire transmission lines. For example, athree-dimensional underground electromagnetic array may be constructedas a single two-wire transmission lines as shown in FIG. 1. Or thesethree-dimensional underground electromagnetic arrays may be constructedof a number of two-wire transmission lines. This would be a 2 by mthree-dimensional underground electromagnetic array. More generally theycan be an n row by m column structure as noted in the paragraph above.These three-dimensional underground electromagnetic arrays can be eitherstatic or mobile. Static three-dimensional underground electromagneticarrays are constructed from well pipe lengths and are inserted into thewell borehole in the same method as normal well pipe. Mobilethree-dimensional underground electromagnetic arrays are simple largediameter wires inserted into specially designed RF transparent wellpipe. The outer diameter is set by the condition that there should besufficient space for oil and gas to flow around the wire. Bothembodiments will be described in more detail later.

The RF energy, produced above ground in RF generators 102, is guided toone of the three-dimensional underground electromagnetic arrays wherethe energy is deposited into hydrocarbon bearing strata 126 viaspecially designed center conductor RF transmission lines 104, 106. RFgenerators 102 are within current industry standard manufacturingcapability. RF generators 102 are used to convert local power into RFpower. This process can be fed from green sources such as wind and solarto reduce the system carbon footprint. Each individual horizontal wellpipe has its own center conductor RF transmission line 104, 106 and RFcoupler, as will be described in greater detail later. Each is phasecontrolled to apply RF energy in the proper fashion so that guidingoccurs and that heating occurs in the proper locations in hydrocarbonbearing strata 126.

The energy from RF generators 102 is fed into specialized RF centerconductor transmission lines 104, 106. The specially designed centerconductor RF transmission lines 104, 106 are beyond current industrypractice because they are intended to be used in high temperature dirtyenvironments, should have significant tensile strength, should carrylarge amounts of power, and should mate with hydrocarbon lock 108 toprevent the inadvertent escape of hydrocarbon gases and liquids. Sincethe wavelength of the RF energy far exceeds the diameter of the wellpipe, the likely solution for guiding energy to an RF coupler is centerconductor RF transmission line 104, 106, though other solutions arepossible. This center conductor RF transmission line 104, 106 will beunique for multiple reasons as follows.

Center conductor RF transmission lines 104, 106 should be capable ofcarrying high power, 50 KW to 500 KW, at very low loss so that RF energycan be transported over long distances.

Center conductor RF transmission lines 104, 106 should be capable offunctioning in a high temperature environment, approaching 600° Celsius.Special high temperature, low loss dielectrics should be used such asthe Hotblox series 700 high dielectric from ATC materials.

Center conductor RF transmission lines 104, 106 should be able tofunction in dirty environments so several new features are needed. Firsta foreign material barrier is required at each end of sections of centerconductor RF transmission lines 104, 106. This barrier should becomposed of high temp, low loss dielectric and should prevent anyforeign objects or fluids from getting into center conductor RFtransmission lines 104, 106. Further there will be a recessed port inthe steel pipe that allows access to the volume at the connection pointbetween center conductor RF transmission lines 104, 106 sections. Thiswill allow sensing of the volume to ensure no foreign objects arepresent, and the ability to both evacuate the section and refill thesection full of dry air/nitrogen.

Center conductor RF transmission lines 104, 106 should be capable ofsupporting their own weight over large vertical drops while supportedsolely from the highest vertical point. External strengthening membersshould not be used since the outer surface of the conductor should besmooth to prevent snagging or catching while in use. Center conductor RFtransmission lines 104, 106 transmission may include steel casing, innercopper liner, and center conductor also composed of copper. The size ofthe outer steel cylinder would be set to allow center conductor RFtransmission lines 104, 106 to support their own weight over a 5000 ft.vertical drop. The copper pipe would be attached to the inner walls ofthe steel pipe to ensure they both stretch equally under load. The outerdiameter of the steel pipe used to strengthen the center conductor RFtransmission lines 104, 106 is sized to ensure that sufficient area forproduct flow up the well bore exists.

Center conductor RF transmission lines 104, 106 should minimize theblockage in the well pipe to allow product to flow freely. This means aspecialized connection system with minimal flange dimensions. The outersurface is a smooth cylinder to prevent snagging or catching whileinserting or withdrawing center conductor RF transmission lines 104,106. This same cylindrical cross section allows mating with hydrocarbonlock 108 for inserting or retracting additional pieces of centerconductor RF transmission lines 104, 106. One way to accomplish this isby using threaded pipe fittings instead of flange connections on centerconductor RF transmission lines 104, 106. The procedures for insertingor retracting additional lengths of center conductor RF transmissionlines 104, 106 should be very similar to the procedure for insertingnormal well pipe production casing so it will be familiar to the wellcrew. The main difference will be the joint integrity check that isperformed after each joint is made.

The RF energy couples into hydrocarbon bearing strata 126 bydielectrically heating any molecule that has a dipole moment. Thethree-dimensional underground electromagnetic array and center conductorRF transmission lines 104, 106 are coupled to each other using speciallydesigned RF couplers, which are described in more detail in FIG. 2.

FIG. 2 illustrates a portion of vertical well pipe 114 and well pipes110 and 112 of FIG. 1 between double arrows AA and BB.

As shown in FIG. 2, dry fracture shale energy extraction systemadditionally includes a primary-phase RF coupler 202 and asecondary-phase RF coupler 204.

Primary-phase RF coupler 202 is electrically connected to primary-phasecenter conductor RF transmission line 104. Primary-phase RF coupler 202is disposed within primary-phase well pipe 110. Secondary-phase RFcoupler 204 is electrically connected to secondary-phase centerconductor RF transmission line 106. Secondary-phase RF coupler 204 isdisposed within secondary-phase well pipe 112.

Primary-phase RF coupler 202 may be any device or system, which couplesRF energy from primary-phase center conductor RF transmission line 104to either primary-phase well pipe 110 or to secondary-phase coupler 204.Secondary-phase RF coupler 204 may be any device or system, whichcouples RF energy from secondary-phase center conductor RF transmissionline 106 to secondary-phase well pipe 112 or to primary-phase coupler202.

In operation, primary-phase RF coupler 202 and secondary-phase RFcoupler 204 connect center conductor RF transmission lines 104, 106 tothe three-dimensional underground electromagnetic array. RF couplers202, 204 guide the energy from RF center conductor transmission lines104, 106 to the three-dimensional underground electromagnetic array withlow loss. All the energy going into the three-dimensional undergroundelectromagnetic array flows through RF couplers 202, 204. There is onecoupler for each line in the three-dimensional undergroundelectromagnetic array since each line is fed by its own RF centerconductor transmission line. It is critical that the couplers have lowloss and low reflection coefficients so that the majority of the energygoes into the three-dimensional underground electromagnetic array and isguided to hydrocarbon bearing strata 126.

RF couplers 202, 204 contain a means to position themselves within thewell bore to optimize coupling, both radially and longitudinally.

It should be noted that all embodiments of RF couplers 202, 204 willhave a disconnect mechanism to allow RF coupler 202, 204 to remain inthe well while center conductor RF transmission line is withdrawn tominimize damage to center conductor RF transmission line in the event RFcouplers 202, 204 become stuck in the well bore.

Also when any of the embodiments of RF coupler 202, 204 are in use,there may exist conditions where oil and gas produced by thethree-dimensional underground electromagnetic array may have to flowpast RF coupler 202, 204 to be recovered above ground. All realizationsof RF coupler 202, 204 include slots or other means to allow movement ofoil and gas past the coupler and through the well bore.

RF couplers 202, 204 include one of many possible realizations, four ofwhich are described herein. The described embodiments are the inductive,capacitive, direct, and three-dimensional underground electromagneticarray leg depending on dry fracture shale energy extraction system 100embodiment and down-hole conditions. When RF couplers are beingdescribed in general, then the number designators 202, 204 will be used.Specific embodiments of the couplers will have their own numberdesignators. These realizations will be discussed later in thedisclosure.

Returning to FIG. 1, the temperature induced effects on bearing strata126 are described in more detail.

As the temperature in hydrocarbon bearing strata 126 rises, three veryimportant effects occur. First stresses are produced within hydrocarbonbearing strata 126. These stresses are caused by thermal gradientswithin hydrocarbon bearing strata 126, and by the differential relativethermal expansion. As hydrocarbon bearing strata 126 heats, the amountof stress increases. The expansion of hot hydrocarbon bearing strata 126is being resisted by the colder surrounding strata putting large volumesof hydrocarbon bearing strata 126 into tension and large volumes intocompression. In regions of tension, when the stresses exceed thecombined fracture strength of the material and the surroundinghydrostatic pressure cracks will form. In regions of compression, cracksform based on the criteria in the well-known Griffith theory for brittlefracture. This criteria is exceeded in the compression region. Entrappedwater is also expanding due to the heating process and will enhance thecracking process.

Three-dimensional finite element computer analysis has shown that dryfracture shale energy extraction system 100 will create fracture stressdistributed throughout the volume in region near the wave guidingsystem, both inside and outside of the guiding structure. Due to theamount of and distribution of stress predicted, dry fracture shaleenergy extraction system 100 is predicted to create a dense crack fieldwithin hydrocarbon bearing strata 126.

The result of this cracking is an increase in the liquid and gaspermeability of hydrocarbon bearing strata 126 allowing the flow of oiland gas to the well pipe. Dry fracture shale energy extraction system100 will provide precise control of stress conditions to maximizecracking and will allow the release of oil & gas from large pay zonesover long periods of time with low life-cycle operating costs and a lowgreenhouse-gas footprint.

Second, hydrocarbon bearing strata 126 goes through an irreversiblephase change, which results in a loss of material strength. This adds tothe amount of cracking and further increases the liquid and gaspermeability of hydrocarbon bearing strata 126.

Third, the kerogen contained within hydrocarbon bearing strata 126 goesthrough in situ pyrolysis and produces high quality oil and gas. Theamount of oil and gas produced is a function of the type and amount ofkerogen present in hydrocarbon bearing strata 126. Because of thepermeability increase discussed above, the oil and gas produced is ableto flow to well pipes 110, 112 and be retrieved at surface of the earth122.

The heating occurs over broad volumes of material. Pyrolysis coke buildup and subsequent clogging around the three-dimensional undergroundelectromagnetic array will not occur since the pyrolysis occursuniformly throughout hydrocarbon bearing strata 126 depending on theamount of kerogen at any particular location. A second coke issue is theincreased conductivity that occurs if the char is heated to high enoughtemperature. If the coke becomes more lossy than the other materials inhydrocarbon bearing strata 126, the coke will be preferentially heatedby the electric fields. Since the highest temperatures will occur withthe highest fields, this means the effect will be greatest close to thewell pipes. This can cause the heating profile to appear more like localresistive heating than distributed field heating. To prevent this localheating effect, the process will be monitored and carefully controlledto ensure temperatures never reach the levels where the coke becomesconductive enough to affect the process.

Dry fracture shale energy extraction system 100 can also be used toenhance the production of wells in heavy oil and oil sands with slightmodifications to prevent pyrolysis char from clogging the product accessto the well pipe.

Many embodiments of dry fracture energy extraction system 100 arepossible. Two are described next.

In the first embodiment of the present invention, specialized well pipesare used, which are RF transparent while still providing the requiredstrength to stabilize the well bore. These are discussed in more detailFIGS. 3a, 3b and 4.

FIGS. 3a-b illustrate the movement of RF couplers 303, 412 (shown inFIG. 4) within the RF transparent well pipe.

FIG. 3a illustrates position 302 of primary-phase RF transparent wellpipe coupler 303 within a primary-phase RF transparent well pipe 304 attime t₁. It also shows the length L of primary-phase RF transparent wellpipe coupler 303.

Primary-phase RF transparent well pipe coupler 303 is connected toprimary-phase center conductor RF transmission line 104. It is alsoelectrically connected to secondary-phase RF transparent well pipecoupler 412 shown in FIG. 4. Primary-phase RF transparent well pipe 304is connected to vertical well pipe 114.

Primary-phase RF transparent well pipe coupler 303 may be any device orsystem, which acts as one leg of a two-wire transmission line, whereincenter conductor RF transmission line 104 is able to transmit an RFsignal having a primary phase as a function of time. Primary-phase RFtransparent well pipe 304 may be any device or system, which allows theRF energy to pass unimpeded from primary-phase RF transparent well pipecoupler 303 into hydrocarbon bearing strata 126.

FIG. 3b illustrates position 306 of primary-phase RF transparent wellpipe coupler 303 within primary-phase RF transparent well pipe 304 attime t₂.

In operation the couplers themselves form the legs of thethree-dimensional underground electromagnetic array. Thethree-dimensional underground electromagnetic array is moved fromposition 302 at time t₁ to position 306 at time t₂ by simply moving thelocation of all the couplers from location 302 at time t₁ to location306 at time t₂.

The length L of primary-phase RF transparent well pipe coupler 303 willbe set based on optimizing the system for a certain amount of oil andgas output as a function of time. The optimization parameters includethe electrical properties of hydrocarbon bearing strata 126, the amountof hydrocarbon bearing strata 126 desired to be heated, the desiredfinal temperature, the time period allotted for heating, and the amountof RF power available.

The relative placement of primary-phase RF transparent well pipe coupler303 and secondary-phase RF coupler 412 within the RF transparent wellpipes will be further described with reference to FIG. 4.

FIG. 4 illustrates primary-phase RF transparent well pipe 304, asecondary-phase RF transparent well pipe 410, and a heating zone 402around primary-phase RF transparent well pipe coupler 303 andsecondary-phase RF transparent well pipe coupler 412 at time t₁.

As shown in the figure, overall heating zone 402 includes an upperheating zone 404, a middle heating zone 406 and a lower heating zone408. Additionally shown is a secondary-phase RF transparent well pipe410 secondary-phase RF transparent well pipe coupler 412.

RF heating zones 404, 406 and 408, form contiguous heating zone 402surrounding RF transparent well pipes 410 and 304. Primary-phase RFtransparent well pipe coupler 303 is disposed within primary-phase RFtransparent well pipe 304. Secondary-phase RF transparent well pipecoupler 412 is disposed within secondary-phase RF transparent well pipe410. RF couplers 303 and 412 are electrically connected via theelectromagnetic fields.

Primary-phase RF transparent well pipe coupler 303 and secondary-phaseRF coupler 412 are acting as the two-wires of a twin wire transmissionline in a lossy media, hydrocarbon bearing strata 126. RF heating zone402 is being heated by the fields generated around primary-phase RFtransparent well pipe coupler 303 and secondary-phase RF transparentwell pipe coupler 412. RF transparent well pipe 410 may be any device orsystem, which allows unimpeded flow of RF energy from secondary-phase RFtransparent well pipe coupler 412 into hydrocarbon bearing strata 126,wherein center conductor RF transmission line 106 is able to transmit anRF signal having a secondary phase as a function of time, and whereinthe primary-phase is 180° out of phase with respect to thesecondary-phase.

In operation, RF transparent well pipe couplers themselves 303, 412 formthe legs of a twin wire transmission line and hence two of the legs ofthe three-dimensional underground electromagnetic array. They can beplaced anywhere along the underground set of RF transparent well pipesto heat hydrocarbon bearing strata 126. The position of thethree-dimensional underground electromagnetic array is changed by eitheradding or removing sections of center conductor RF transmission lines104, 106. This allows precise placement of the three-dimensionalunderground electromagnetic array within hydrocarbon bearing strata 126and hence precise control of the heating process. RF transparent wellpipe couplers 303, 412 have small enough diameters to allow oil and gasfrom previously heated sections of hydrocarbon bearing strata 126 topass by RF transparent well pipe couplers 303, 412 and rise to surfaceof the earth 122 for recovery. While not specifically required for thisdesign, it is likely that all RF transparent well pipe couplers 303, 412will have the same length L.

The three-dimensional underground electromagnetic array is built arounda set of parallel well holes. This means RF transparent well pipecouplers 303, 412 will be parallel to each other. The most likelyconfiguration will be that RF transparent well pipe couplers 303, 412are both located at the same horizontal section of the well pipe.However the exact offset, if any, will be based on optimization duringthe heating process.

The second embodiment of the invention is now described with referencesto FIGS. 5a, 5a , 6 and 7, In this embodiment the well pipe itself isused as the wires of a two-wire transmission line. Multiple two-wiretransmission lines form a three-dimensional underground electromagneticarray. For clarity, the disclosure primarily discusses groups oftwo-wire transmission lines as the basic building block of thethree-dimensional underground electromagnetic arrays. However othermultiwire transmission lines, for example the five wire transmission,will work also.

The well pipe is divided into longitudinal sections by non-conductingspacers hence forming a set of three-dimensional undergroundelectromagnetic arrays along the horizontal length of the well bore.Unlike the previous embodiment this set of three-dimensional undergroundelectromagnetic arrays are located at fixed positions along thehorizontal length of the well pipes.

FIGS. 5a and 5b illustrate the movement of RF couplers 202, 204 withinthe segmented well pipe.

FIG. 5a illustrates primary-phase RF coupler 202 placement within aprimary-phase segmented well pipe 500 at time t₃, in accordance withaspects of the present invention.

As shown in the figure, primary-phase segmented well pipe 500 includes aconductive segment 502, a dielectric spacer 504 and a conductive segment506.

Conductive segment 502 is connected to one end of dielectric spacer 504.The other end of dielectric spacer 504 is connected to conductivesegment 506. Primary-phase RF coupler 202 is electrically connected toconductive segment 502. Non limiting examples of such a connection areinductive, capacitive, and direct connections.

Primary-phase RF coupler 202 conducts RF energy into conductive segment502. Conductive segment 502 may be any device or system, which acts asthe primary-phase wire for a two-wire transmission line. Dielectricspacer 504 may be any device or system, which electrically disconnectsconductive segment 502 from conductive segment 506. Conductive segment506 may be any device or system, which will be activated as theprimary-phase wire for a two-wire transmission line at a different timein the heating process.

FIG. 5b illustrates another location for primary-phase RF coupler 202placement within primary-phase segmented well pipe 500 at time t₄, inaccordance with aspects of the present invention.

As shown in the figure, RF coupler 202 is now located within conductivesegment 506.

In operation, RF energy is transmitted down primary-phase centerconductor RF transmission line 104. Primary-phase RF coupler 202receives the energy and forms a match between primary-phase centerconductor RF transmission line 104 and the outside of conductive segment502 at time t₁ and the outside of conductive segment 506 at time t₂.This allows the RF energy to be coupled to different conductive segmentsalong the horizontal section of the well at different times. Matching isrequired to maximize the power delivered to hydrocarbon strata 126 andminimize the reflected signal. The matching will also serve to minimizeevanescent fields and ensure that heating occurs at the desired portionof hydrocarbon bearing strata 126.

Typically one three-dimensional underground electromagnetic array isenergized at a time. The three-dimensional underground electromagneticarray is energized by locating RF couplers 202, 204 at the locationwhere dielectric spacers (e.g. 504) connect to conductive segments (e.g.506) for all legs of the three-dimensional underground electromagneticarray that are at the same horizontal position along the well bore.

A segmented well pipe of the second embodiment of the present inventionmay be composed of alternating sections of conductive well pipe anddielectric spacers. This will be further described with reference toFIG. 6.

FIG. 6 illustrates a primary-phase segmented well pipe section 600between double arrows CC and DD in FIG. 1 in accordance with aspects ofthe present invention.

As shown in FIG. 6, segmented well pipe section 600 includes conductivesegment 502, conductive segment 506, a conductive segment 604, aconductive segment 608, a conductive segment 612, dielectric spacer 504,a dielectric spacer 602, a dielectric spacer 606, and a dielectricspacer 610. Also shown in the figure are conductive well pipe segmentlength D, and dielectric spacer length d.

Conductive segment 502 is connected to dielectric spacer 504. Dielectricspacer 504 is connected between conductive segment 502 and conductivesegment 506. Conductive segment 506 is connected between dielectricspacer 504 and dielectric spacer 602. Dielectric spacer 602 is connectedbetween conductive segment 506 and conductive segment 604. Conductivesegment 604 is connected between dielectric spacer 602 and dielectricspacer 606. Dielectric spacer 606 is connected between conductivesegment 604 and conductive segment 608. Conductive segment 608 isconnected between dielectric spacer 606 and dielectric spacer 610.Dielectric spacer 610 is connected between conductive segment 608 andconductive segment 612. Conductive segment 612 is connected todielectric spacer 610. Primary-phase RF coupler 202 is electricallyconnected to conductive segment 608.

Conductive segment 604 may be any device or system, which acts as theprimary-phase wire for a two-wire transmission line but is not activatedin the figure. Conductive segment 608 may be any device or system, whichacts as the primary-phase wire for a two-wire transmission line. It isactivated by an electrical connection with primary-phase RF coupler 202.Conductive segment 612 may be any device or system, which acts as theprimary-phase wire for a two-wire transmission line but is not activatedin the figure. Dielectric spacer 602 may be any device or system, whichelectrically disconnects conductive segment 506 from conductive segment604. Dielectric spacer 606 may be any device or system, whichelectrically disconnects conductive segment 604 from conductive segment608. Dielectric spacer 610 may be any device or system, whichelectrically disconnects conductive segment 608 from conductive segment612.

In operation, conductive segments as disclosed herein are energized atparticular times in the heating process. They may be energizedsequentially along the horizontal well bore or not depending on how theheating is managed and optimized along the well bore.

The length D of conductive segments, as disclosed herein, will be setbased on optimizing the system for a certain amount of oil and gasoutput as a function of time. The optimization parameters include theelectrical properties of hydrocarbon bearing strata 126, the amount ofhydrocarbon bearing strata 126 desired to be heated, the desired finaltemperature, the time period allotted for heating, and the amount of RFpower available. Length D can also be variable along the length of thewell bore although all segments at a given horizontal position willlikely have the same length.

Dielectric spacers, as described herein, will be used to electricallyseparate conductive segments, as described herein, from each other.

Dielectric spacers, as described herein, can also provide windows for RFpenetration through the steel well pipe production casing.

Dielectric spacers, as described herein, are short, high temperature,high strength pipes with controllable electrical properties that willvary as a function of radial and longitudinal location in the dielectricspacers. Dielectric spacers will thread directly onto conductivesegments, as described herein, so that the process for insertingproduction casing into the wells is not changed.

Dielectric spacers, as described herein, can also provide the RFcoupling technology depending on the type of coupling used. In thedirect coupling, capacitive coupling, and inductive couplingrealizations of RF couplers 202, 204 there will need to be matingsurfaces in the dielectric spacer. In all coupling cases there may beconductive structures inside dielectric spacer to facilitate thecoupling of the RF energy to the outside of well pipe segments (e.g.502, 506).

Dielectric spacers, as described herein, need to have sufficient tensilestrength to support steel well pipe of a length equal to the entirevertical section of the well. Dielectric spacers will only be needed inthe horizontal section of the well for operation of the system so afterinsertion the spacers will no longer be subject to large tensile loads.After the well pipe is in place, dielectric spacers will be subject tohigh temperatures (up to 600° Celsius) and should maintain a largeportion of their strength to prevent well collapse.

The length d of the dielectric spacers, as described herein, is based onachieving the desired electrical separation between adjacentthree-dimensional underground electromagnetic arrays.

The relative placement of primary-phase RF coupler 202 andsecondary-phase RF coupler 204 within primary-phase and secondary-phasesegmented well pipes will now be described with reference to FIG. 7.

FIG. 7 illustrates both primary-phase segmented well pipe section 600and secondary-phase segmented well pipe section 700 between doublearrows CC and DD in FIG. 1, in accordance with aspects of the presentinvention.

As shown in FIG. 7, secondary-phase segmented well pipe section 700includes a conductive segment 702, a conductive segment 706, aconductive segment 710, a conductive segment 714, a conductive segment718, a dielectric spacer 704, a dielectric spacer 708, a dielectricspacer 712, and a dielectric spacer 716. Also shown are segmented wellpipe section 600 and heating zone 720.

Conductive segment 702 is connected to dielectric spacer 704. Dielectricspacer 704 is connected between conductive segment 702 and conductivesegment 706. Conductive segment 706 is connected between dielectricspacer 704 and dielectric spacer 708. Dielectric spacer 708 is connectedbetween conductive segment 706 and conductive segment 710. Conductivesegment 710 is connected between dielectric spacer 708 and dielectricspacer 712. Dielectric spacer 712 is connected between conductivesegment 710 and conductive segment 714. Conductive segment 714 isconnected between dielectric spacer 712 and dielectric spacer 716.Dielectric spacer 716 is connected between conductive segment 714 andconductive segment 718. Conductive segment 718 is connected todielectric spacer 716. Primary-phase conductive segment 506 iselectrically connected to secondary-phase conductive segment 706.

Segmented well pipe section 600 is parallel or nearly parallel withsegmented well pipe section 700 throughout the heated volume inhydrocarbon bearing strata 126.

RF heating zones 722, 724 and 726, form contiguous heating zone 720surrounding conductive segment 506 in primary-phase segmented well pipe600 and conductive segment 706 in secondary-phase segmented well pipe700.

Conductive segment 702 may be any device or system, which acts as thesecondary-phase wire for a two-wire transmission line but is notactivated in the figure. Conductive segment 706 may be any device orsystem, which acts as the secondary-phase wire for a two-wiretransmission line. It is activated by an electrical connection withsecondary-phase RF coupler 204. Conductive segment 710 may be any deviceor system, which acts as the secondary-phase wire for a two-wiretransmission line but is not activated in the figure. Conductive segment714 may be any device or system, which acts as the secondary-phase wirefor a two-wire transmission line but is not activated in the figure.Conductive segment 718 may be any device or system, which acts as thesecondary-phase wire for a two-wire transmission line but is notactivated in the figure.

Dielectric spacer 704 may be any device or system, which electricallydisconnects conductive segment 702 from conductive segment 706.Dielectric spacer 708 may be any device or system, which electricallydisconnects conductive segment 706 from conductive segment 710.Dielectric spacer 712 may be any device or system, which electricallydisconnects conductive segment 710 from conductive segment 714.Dielectric spacer 716 may be any device or system, which electricallydisconnects conductive segment 714 from conductive segment 718.

Heating zone 720 converts kerogen in hydrocarbon bearing strata 126 tooil and gas.

In operation, groups of horizontal production casings at a particularhorizontal location make up the three-dimensional undergroundelectromagnetic arrays. These three-dimensional undergroundelectromagnetic arrays are separated from each other along thehorizontal extent of hydrocarbon bearing strata 126 by dielectricspacers (e.g. 504) placed in each individual well bore. Thethree-dimensional underground electromagnetic arrays are used to guideRF energy to the desired locations in hydrocarbon bearing strata 126. RFcouplers 202, 204 are movable along the well bore and will be used toenergize different three-dimensional underground electromagnetic arrays(groups of lateral well segments) at different times. Both RF couplers202, 204 and dielectric spacers (e.g. 504) are new and designedspecifically for dry fracture shale energy extraction system 100.

Returning to FIG. 1, production casing is inserted after well drillingis complete. As the casing is being inserted, dielectric spacers (e.g.504) are attached between casings every XX casings. The number XX ofcasings is determined based on the electromagnetic properties ofhydrocarbon bearing strata 126 being heated, the amount of hydrocarbonbearing strata 126 to be heated, the desired final temperature, the timeperiod allotted for heating, the frequency of operation, and the RFpower available, and can be anywhere from between every 20 casings toevery casing. As an example, for a 5000 ft horizontal run with theproduction casings separated by dielectric spacers every 300 ft, therewill be approximately 16 three-dimensional underground electromagneticarrays.

This process can also work with preexisting well casing by cutting outsegments of the well casing to get electrical isolation. These cuts aremade at specific points along the horizontal extent of the well fieldbased on the on the electromagnetic properties of hydrocarbon bearingstrata 126 being heated, the frequency of operation, and the RF poweravailable.

The actual three-dimensional underground electromagnetic arrayconfiguration can take many forms depending on the electromagneticproperties of hydrocarbon bearing strata 126 being heated, the amount ofhydrocarbon bearing strata 126 to be heated, the desired finaltemperature, the time period allotted for heating, the frequency ofoperation, and the RF power available. Possible three-dimensionalunderground electromagnetic array configurations are discussed in moredetail for FIG. 8.

FIGS. 8a-e illustrate several examples of the many possible well pipegeometric configurations in accordance with aspects of the presentinvention. They show end on views of the three-dimensional undergroundelectromagnetic array; the well pipes are oriented perpendicular to thepage.

As shown in FIG. 8a , a two-wire transmission line 800 includesprimary-phase well pipe 110 and secondary-phase well pipe 112, inaccordance with aspects of the present invention.

Primary-phase transmission line conductor associated with primary-phasewell pipe 110 is electrically coupled to secondary-phase transmissionline conductor associated with secondary-phase well pipe 112.Primary-phase well pipe 110 is parallel or nearly parallel tosecondary-phase well pipe 112 throughout the heated volume inhydrocarbon bearing strata 126.

As shown in FIG. 8b , a four-wire transmission line 802 is formed fromwell pipes, in accordance with aspects of the present invention.

All the transmission line conductors associated with well pipes in thefigure are electrically coupled to each other. All the well pipes areparallel or nearly parallel throughout the heated volume in hydrocarbonbearing strata 126.

Each of the wires in the figure is either a primary-phase orsecondary-phase conductor of the transmission line.

As shown in FIG. 8c , a rectangular, six-wire transmission line 804 isformed from well pipes, in accordance with aspects of the presentinvention.

All the transmission line conductors associated with well pipes in thefigure are electrically coupled to each other. All the well pipes areparallel or nearly parallel throughout the heated volume in hydrocarbonbearing strata 126.

Each of the wires in the figure is either a primary-phase orsecondary-phase conductor of the transmission line.

As shown in FIG. 8d , a square, nine-wire transmission line 806 isformed from well pipes, in accordance with aspects of the presentinvention.

All the transmission line conductors associated with well pipes in thefigure are electrically coupled to each other. All the well pipes areparallel or nearly parallel throughout the heated volume in hydrocarbonbearing strata 126.

Each of the wires in the figure is either a primary-phase orsecondary-phase conductor of the transmission line.

As shown in FIG. 8e , a five-wire transmission line 808 is formed fromwell pipes, in accordance with aspects of the present invention.

All the transmission line conductors associated with well pipes in thefigure are electrically coupled to each other. All the well pipes areparallel or nearly parallel throughout the heated volume in hydrocarbonbearing strata 126.

Each of the wires in the figure is either a primary-phase orsecondary-phase conductor of the transmission line.

The number, spacing, and geometry of the wells is determined in advanceto be the most economically favorable geometry based on the desiredblock size to heat, the dimensions of hydrocarbon bearing strata 126,the electrical, mechanical, and thermal properties of the strata, andthe desired output of oil and gas from the system. The wells are drilledat prescribed distances from each other and the floor of hydrocarbonbearing strata 126. The wells will likely be oriented parallel to thebedding planes in hydrocarbon bearing strata 126 and so can vary fromhorizontal to many degrees from horizontal.

Returning to FIG. 1, a brief description of the heating process will beprovided. A longer version of the description is provided following FIG.15. The heating process is optimized based on the particular electrical,mechanical and chemical properties of hydrocarbon strata 126 to beheated. No two hydrocarbon strata 126 are identical so a differentprocess will be developed and optimized for the each strata in which thesystem is to work. An example process is given next.

The example process starts by connecting RF couplers 202, 204 to thethree-dimensional underground electromagnetic array closest to verticalwell pipe section 114. This particular three-dimensional undergroundelectromagnetic array is energized for a period of 1 to 15 monthsdepending on the volume of hydrocarbon bearing strata 126 associatedwith the three-dimensional underground electromagnetic array, the amountof RF power available, the frequency of the RF power and the losstangent of hydrocarbon bearing strata 126. During this time hydrocarbonbearing strata 126 is retorted, stressed, and cracked. The gas and oilpreexisting within hydrocarbon bearing strata 126, plus the additionaloil and gas from retorting, flow through the new cracks in hydrocarbonbearing strata 126 and up the well pipes for recovery.

When hydrocarbon bearing strata 126 reaches an average temperature ofapproximately 350° Celsius, in situ retorting will be complete and RFcouplers 202, 204 are moved to the next three-dimensional undergroundelectromagnetic array in the series. While the second volume ofhydrocarbon bearing strata 126 is heating up, the firstthree-dimensional underground electromagnetic array volume continues toproduce. It may be necessary to re-energize the first three-dimensionalunderground electromagnetic array to reopen cracks and produce newcracks as hydrocarbon bearing strata 126 cools.

The location of RF couplers 202, 204 within the well pipe is adjusted byadding or removing sections of center conductor RF transmission lines104, 106. This connection is made above ground level in the same manneras well pipe casings are attached to a well string. Each piece ofadditional section of center conductor RF transmission lines 104, 106 isattached with threads to the one already partially inserted into thewell. The entire center conductor RF transmission line string is thenlowered further into the well until it reaches the point where the nextpiece of center conductor RF transmission line can be attached.Retracting RF couplers 202, 204 is the reverse of this process.

A major difference between dry fracture shale energy extraction system100 and all the other mechanisms described is that dry fracture shaleenergy extraction system 100 is designed around a series ofthree-dimensional underground electromagnetic arrays that are energizedin a specific fashion. This method of heating causes cracks in thedesired location with the desired orientation, causes efficient in situconversion of kerogen to high quality oils and gas, and results in theproduction a consistent flow of product for many years.

A comparison to hydraulic fracturing is given next. Hydraulicfracturing, or fracking, is used to access the oil gas that has alreadybeen produced over millions of years by the natural start of thepyrolysis process. The amount of retrieval is typically less than 10%.Dry fracture shale energy extraction system 100 will return a largeramount of product per unit volume of hydrocarbon bearing strata 126 thanhydraulic fracturing for two reasons. Firstly, it will return both thegas and oil already present and the produced oil and gas formed frompyrolysis of the kerogen in hydrocarbon bearing strata 126. The producedoil and gas is not present for the fracking process to remove. Secondly,the drainage volume each well pipe accesses is much smaller for dryfracture shale energy extraction system 100 than for fracking. Thismeans better drainage for a smaller volume. Better oil and gas drainagewill allow a higher percentage of overall product retrieval, likelygreater than 50%.

The well pads for dry fracture shale energy extraction system 100 willbe prepared in the same manner as typical well pads with a couple ofexceptions. There will be an RF generator hut, which protects RFgenerators such as RF generator 102 and associated control circuitry. Aspecialized structure will be required for inserting or retractingcenter conductor RF transmission lines 104, 106 down the well bore. Thisstructure will closely resemble existing site hardware that is used forinserting or retracting small diameter well pipe.

The oil and gas will be at elevated temperatures, up to 350° Celsius,when they arrive at surface of the earth 122. An air based chiller willbe used to cool the product prior to shipping the product to therefinery.

As described above, RF couplers 202, 204 for the segmented conductivewell pipe embodiment form the junction between center conductor RFtransmission lines 104, 106 and conductive segments of well pipe (e.g.502, 506), and are described in more detail in FIGS. 9-13.

FIGS. 9-13 illustrate non-limiting example coupling arrangements(direct, inductive, and capacitive) to conduct the RF energy from centerconductor RF transmission lines 104, 106 on to the first andsecondary-phase segmented well pipe sections 600 and 700 as an exampleof what could be used in the second embodiment of the present invention.

An example direct connection scheme for guiding the RF energy onto theoutside of conductive segments (e.g. 502, 506) of the segmented wellpipe sections 600, 700 will now be described with reference to FIG. 9.

FIG. 9 illustrates an example direct connection RF coupler 900, inaccordance with aspects of the present invention.

As shown in the figure, direct connection RF coupler 900 includes aconnection point 902 to primary-phase center conductor RF transmissionline 104, a conductor 904, and a conducting shoe 906. Additionally shownin the figure are center conductor 908 of primary-phase center conductorRF transmission line 104, a conducting ring 910, and a conducting ring912.

Connection point 902 is electrically connected to center conductor 908of primary-phase center conductor RF transmission line 104 and Conductor904. Conductor 904 is electrically connected to conducting shoe 906.Conducting shoe 906 makes direct electrical contact with conducting ring910. Conducting ring 910 is located within dielectric spacer 504 and iselectrically connected to conductive segment 506 of primary-phasesegmented well pipe 600. Conducting ring 912 is located withindielectric spacer 504 and is electrically connected to conductivesegment 502 of primary-phase segmented well pipe 600. These componentsare disposed within primary-phase segmented well pipe section 600. Asecond set of these components is disposed within secondary-phasesegmented well pipe section 700.

Connection point 902 may be any device or system, which connects RFenergy from center conductor 908 of primary-phase center conductor RFtransmission line 104 to Conductor 904. The input impedance ofconnection point 902 should matches primary-phase center conductor RFtransmission line 104 to maximize energy transfer. Matching ismaintained over a range of electrical parameters as hydrocarbon bearingstrata 126 heats and the material properties change. Conductor 904 maybe any device or system that guides RF energy to conducting shoe 906.Conducting shoe 906 may be any device or system, which makes directphysical and electrical contact with conducting ring 910 in dielectricspacer 504. The mechanical and electrical connection is maintained inthe oil, gas, and saltwater environment that may exist in the well.Conducting ring 910 in dielectric spacer 504 may be any device orsystem, which passes RF energy on to conductive segment 506 ofprimary-phase segmented well pipe 600. Conducting ring 912 may be anydevice or system, which may be used when connecting to conductivesegment 502 and will be discussed later. All components are capable ofwithstanding the downhole environment, which includes high pressures,temperatures and possibly chemically corrosive materials.

In operation, direct connection RF coupler 900 is the matching systembetween center conductor RF transmission lines 104, 106 and thesegmented well pipe sections 600, 700. Direct connection RF coupler 900will guide the RF waves with low loss and minimal reflection onto theoutside of a segment of the segmented well pipe 600, 700. As a group thecouplers will also launch the wave onto the three-dimensionalunderground electromagnetic array with minimal loss to unwantedradiative electromagnetic fields.

FIG. 10-12 illustrate the details of an inductive coupler and how it maybe positioned with respect to a dielectric spacer in accordance withaspects of the present invention.

FIG. 10 illustrates an example inductive RF coupler 1000, in accordancewith aspects of the present invention.

As shown in the figure, inductive RF coupler 1000 includes an inductivecoil 1002, a return connection 1004 to outer conductor 1018 of a centerconductor 908 of primary-phase center conductor RF transmission line104, a ferrous core 1006, a conductor 1008, an expandable end piece1010, and a dielectric cover 1012. Also shown in the figure is an RFtransmission line outer conductor 1014.

The left side of inductive coil 1002 is electrically connected to centerconductor 908 of primary-phase center conductor RF transmission line104. The right side of inductive coil 1002 is electrically connected toRF transmission line outer conductor 1014 of primary-phase centerconductor RF transmission line 104 by return connection 1004. Inductivecoil 1002 is also connected to ferrous core 1006 by magnetic fields.Ferrous core 1006 is connected to conducting ring 910 by conductor 1008.Conducting ring 910 is electrically connected to conductive segment 506of primary-phase segmented well pipe 600. These components are alldisposed within primary-phase segmented well pipe section 600. A secondset of these components is disposed within secondary-phase segmentedwell pipe section 700 (not shown).

Inductive coil 1002 may be any device or system, which magneticallycouples and matches and RF energy from primary-phase center conductor RFtransmission line 104 to ferrous core 1006. The input impedance ofinductive RF coupler 1000 matches primary-phase center conductor RFtransmission line 104 to maximize energy transfer. Matching ismaintained over a range of electrical parameters as hydrocarbon bearingstrata 126 heats and the material properties change. Return line 1004may be any device or system, which completes the electrical circuitbetween inductive coil 1002 and RF transmission line outer conductor1014 of primary-phase center conductor RF transmission line 104.

Ferrous core 1006 may be any device or system, which receives RF energyfrom inductive coil 1002. Conductor section 1008 may be any device orsystem, which guides RF energy out to conducting ring 910. Expandableend piece 1010 may be any device or system that makes a securemechanical connection to conductive segment 506 of primary-phasesegmented well pipe 600. The mechanical and electrical connection ismaintained in the oil, gas, and saltwater environment that may exist inthe well. Dielectric cover 1012 may be any device or system, whichprotects inductive coil 1002 and ferrous core 1006 from the down-holeenvironment, which may include hot oil, gas, water.

Conducting ring 910 may be any device or system that forms a smoothconnection for currents flowing out onto conductive segment 506 ofprimary-phase segmented well pipe 600. Conducting ring 912 may be anydevice or system, which forms a smooth connection for currents flowingout onto conductive segment 502 of primary-phase segmented well pipe 600when conductive segment 502 is activated. RF transmission line outerconductor 1014 may be any device or system, which forms the outer shieldfor primary-phase center conductor RF transmission line 104. Allcomponents should be capable of withstanding the downhole environment,which includes high pressures, temperatures and possibly chemicallycorrosive materials.

FIG. 11 illustrates inductive RF coupler 1000 connected to conductivesegment 502 of primary-phase segmented well pipe 600, in accordance withaspects of the present invention.

In operation RF coupler 1000, as shown in FIG. 10 and FIG. 11, may beconnected to either end of a leg of the three dimensional undergroundelectromagnetic array and forms the matching system to efficientlyconduct the RF energy with minimal loss and reflection. RF energytherefore may be guided into either end of the three dimensionalunderground electromagnetic array. This flexibility allows the heatingalong the three dimensional underground electromagnetic array to be moreuniform.

FIG. 12 illustrates inductive coupler 1000 connected to both conductivesegment 502 and conductive segment 506 of primary-phase segmented wellpipe 600, in accordance with aspects of the present invention.

In operation, inductive RF coupler 1000 is the matching system betweencenter conductor RF transmission lines 104, 106 and the segmented wellpipe sections 600, 700. Inductive RF coupler 1000 will guide the RFwaves with low loss and minimal reflection onto the outside of a segmentof the segmented well pipe 600, 700. As a group the couplers will alsolaunch the wave onto the three-dimensional underground electromagneticarray with minimal loss to unwanted radiative electromagnetic fields.

Inductive RF coupler 1000 can be realized in two length regimes based onthe desired use. The “short” version is designed so that only oneconductive segment (e.g. 502) is energized at one time. The “long”version is designed so that inductive RF coupler 1000 can connect toboth sides simultaneous and hence energize the legs of two separatethree-dimensional underground electromagnetic arrays at the same time.Conversely, inductive RF coupler 1000 can be made in only one length andthe length of dielectric spacer (e.g. 504) can be varied. Note thatshort and long are relative terms, the exact lengths of all componentsare governed by the physical properties of hydrocarbon bearing strata126 and the desired oil and gas output as a function of time.

A non-limiting example capacitive connection scheme for guiding the RFenergy onto the outside of one of conductive segments (e.g. 502, 506) ofsegmented well pipe will now be described with reference to FIG. 13.

FIG. 13 illustrates an example capacitive RF coupler 1300, in accordancewith aspects of the present invention.

As shown in the figure, capacitive RF coupler 1300 includes a conductor1302, and a capacitive plate 1304. Additionally shown in the figure is adielectric spacer capacitive plate 1306.

Conductor 1302 is electrically connected to center conductor 908 ofprimary-phase center conductor RF transmission line 104 and tocapacitive plate 1304. Capacitive plate 1304 is connected by electricfields to dielectric spacer capacitive plate 1306. Dielectric spacercapacitive plate 1306 is electrically connected to conductive segment506 of primary-phase segmented well pipe 600. These components aredisposed within primary-phase segmented well pipe section 600. A secondset of these components is disposed within secondary-phase segmentedwell pipe section 700.

Conductor 1302 may be any device or system, which smoothly transitionsthe current from center conductor 908 of primary-phase center conductorRF transmission line 104 to capacitive plate 1304. The input impedanceof capacitive RF coupler 1300 should be matched to primary-phase centerconductor RF transmission line 104 to maximize energy transfer. Matchingshould be maintained over a range of electrical parameters ashydrocarbon bearing strata 126 heats and the material properties change.

Capacitive plate 1304 may be any device or system, which forms one halfof the electric field connection between capacitive RF coupler 1300 anddielectric spacer capacitive plate 1306. Dielectric spacer capacitiveplate 1306 may be any device or system, which forms the other half ofthe electric field connection and also connects the transferred currentsonto conductive segment 506 of primary-phase segmented well pipe 600.Dielectric spacer plate 1306 is only used with the capacitive couplerand is not present in the spacer when inductive or direct connection isused. All components should be capable of withstanding the downholeenvironment, which includes high pressures, temperatures and possiblychemically corrosive materials.

In operation, capacitive RF coupler 1300 is the matching system betweencenter conductor RF transmission lines 104, 106 and the segmented wellpipe sections 600, 700. Capacitive RF coupler 1300 will guide the RFwaves with low loss and minimal reflection onto the outside of a segmentof the segmented well pipe 600, 700. As a group the couplers will alsolaunch the wave onto the three-dimensional underground electromagneticarray with minimal loss to unwanted radiative electromagnetic fields Atunable inductor (not shown) may be used to adjust the coupling toaccount for changing electrical parameters during heating.

Returning to FIG. 1, a discussion of the properties of the undergroundenvironment is provided.

The properties of hydrocarbon bearing strata 126 will change withheating. The most notable change is that, as the water changes to steamand flows out of the well, the imaginary part of the permittivity willdecrease. This will cause less energy to be deposited in spots alreadyheated to the boiling point of water at pressure and more to the coolernearby areas. The boiling point of water increases with pressure so thetemperature at which boiling occurs will be higher the furtherunderground the heating is taking place. As hydrocarbon bearing strata126 is being heated, if the depth is too great there will be no distinctconversion of liquid to gas; water will be in the supercritical state.This pressure is 3200 psi and occurs at a depth of approximately 2750 ftassuming the average density of the rock is 2.6 times the density ofwater. The imaginary part of the permittivity will change throughoutthis range of possible depths and states as the water heats.

Because of this change in electrical properties of hydrocarbon bearingstrata 126, dry fracture shale energy extraction system 100 may employ amatching section (quarter wave or other) between RF coupler 202, 204 andcenter conductor RF transmission line 104, 106 to facilitate thematching between RF generators 102 and the three-dimensional undergroundelectromagnetic array. This may be necessary if the mismatch between thethree-dimensional underground electromagnetic array and center conductorRF transmission line 104, 106 is too large for the tuner associated withRF couplers 202, 204 to compensate for. This will be function of thechanging electrical characteristics of hydrocarbon bearing strata 126.

Two additional systems required for dry fracture shale energy extractionsystem 100 to work are described. FIGS. 14 and 15 detail these ancillarysystems that may facilitate and optimize the use of dry fracture shaleenergy extraction system 100. These systems may be used for bothembodiments of dry fracture shale energy extraction system 100.

FIG. 14 illustrates an example hydrocarbon lock 108 to feed the RF powerdown into the well without loss of oil or gas to the environment, inaccordance with aspects of the present invention.

As shown in the figure, hydrocarbon lock 108 includes a compression bar1402, a compression seal 1404, a hydrocarbon lock body 1406, a pressurereduction pump 1408, a flexible hydrocarbon barrier 1410, and anenvironmental pump 1412.

Compression bar 1402 is located above and connected to compressible seal1404. Compressible seal 1404 is configured within a hole in the top ofhydrocarbon seal body 1406. Hydrocarbon seal body 1406 surroundsprimary-phase center conductor RF transmission line 104, secondary-phasecenter conductor RF transmission line 106 and is connected to the top ofvertical well pipe section 114. Oil recovery pipe 116 passes throughhydrocarbon seal body 1406 and is connected to vertical well pipesection 114. Pressure reduction pump 1408 is connected to oil recoverypipe 116. Flexible hydrocarbon barrier 1410 is connected to the top ofhydrocarbon lock body 1406 on the outside of compressible seal 1404. Theintake to environmental pump 1412 is connected to flexible hydrocarbonseal 1410.

Compression bar 1402 may be any device or system, which compressescompressible seal 1404 to prevent oil and gas leakage during systemoperation. Compressible seal 1404 may be any device or system, whichspreads under compression and seals the ingress point for primary-phasecenter conductor RF transmission line 104 and secondary-phase centerconductor RF transmission line 106.

Hydrocarbon lock body 1406 may be any device or system, which providessupport for compression bar 1402 and compressible seal 1404. Hydrocarbonlock body 1406 also provides the flow path for oil and gas from verticalwell pipe 114 to oil recovery pipe 116.

Pressure reduction pump 1408 may be any device or system, which reducespressure inside of hydrocarbon lock 108 so that, during insertion orretrieval of primary-phase center conductor RF transmission line 104 orsecondary-phase center conductor RF transmission 106 operation, oil andgas are less likely to escape through compressible seal 1404.

Flexible hydrocarbon barrier 1410 may be any device or system, whichprevents any oil or gas that leaks through compression seal 1404 duringhydrocarbon lock operation from escaping into the environment.Environmental pump 1412 may be any device or system, which collects anygas or oil within flexible hydrocarbon seal volume and directs it tostorage tank 118.

All components of hydrocarbon lock 108 should be able to withstand thetemperatures and pressures that will be present from the oil and gascoming up vertical well pipe 114 as the system heats hydrocarbon bearingstrata 126.

In operation hydrocarbon lock 108 will allow the insertion or retractionof several center conductor RF transmission lines 104, 106 from the wellwith no oil or gas leakage. Center conductor RF transmission lines 104,106 are passed through smooth holes in compressible seal 1404 (e.g.valve stem packing or high temperature rubber-like stopper), which forma tight seal when compressed by compression bar 1402 into a conicalseating surface in hydrocarbon lock body 1406 to minimize loss ofproduct and protect the environment. High temperature seating materialsare necessary to withstand the high temp hydrocarbon environment fromthe product flowing up the pipe (˜300 Celsius). When it is necessary tomove center conductor RF transmission lines 104, 106, the sealingpressure is reduced and center conductor RF transmission lines 104, 106will slide freely through the holes in the compressible material.Simultaneously pressure reduction pump 1408 is energized to reduce thepressure in hydrocarbon lock body 1406. While the pressure is reduced,oil and gas will be able to leak at a slow rate through the area aroundcenter conductor RF transmission lines 104, 106. Flexible hydrocarbonbarrier 1410 is applied around hydrocarbon lock 108 to keep any oil orgas from escaping into the environment. When center conductor RFtransmission lines 104, 106 reach the final desired position, thesealing pressure is reapplied.

Hydrocarbon lock 108 will allow the movement of several center conductorRF transmission lines (e.g. center conductor RF transmission lines 104,106) with a no hydrocarbon leakage. The number of center conductor RFtransmission lines is based on the number of horizontal or vertical legsin the well that are energized from a single vertical top section of awell. The configuration shown here is for two center conductor RFtransmission lines 104, 106 though more are possible. The restrictingparameter is the inner diameter of vertical well pipe section 114 beingable to accommodate multiple center conductor RF transmission lines andstill have sufficient cross sectional area to allow product flow.

Center conductor RF transmission lines 104, 106 are passed throughsmooth holes in compressible seal 1404 (e.g. valve stem packing or hightemperature rubber like stopper), which form a tight seal whencompressed by compression bar 1402 into a conical seating surface inhydrocarbon lock body 1406 to minimize loss of product and protect theenvironment. The seal occurs due to the expansion of compressiblematerial 1404 when pressure is applied at the top. This expansion causescompressible material 1404 to tightly seal around center conductor RFtransmission lines hence preventing the escape of oil and gas.

The compressible seal 1404 is composed of material able to withstand thehigh temperature hydrocarbon environment from the product flowing up thepipe (˜300 Celsius). Compressible seal 1404 should be chemically inert.Compressible seal 1404 should also readily expand and compress, evenwhile heated to allow center conductor RF transmission lines 104, 106 tomove. Compressible seal 1404 material should not have significanthysteresis so that the hole size does not remain small when the sealingpressure is reduced.

When it is necessary to move center conductor RF transmission lines 104,106 the sealing pressure is reduced and center conductor RF transmissionlines 104, 106 will slide freely through the holes in compressible seal1404. When center conductor RF transmission lines 104, 106 reach thefinal desired position, the sealing pressure is reapplied. During thetime the pressure is reduced flexible hydrocarbon barrier 1410 willprevent any oil or gas from escaping into the environment. Flexiblehydrocarbon barrier 1410 is clamped to center conductor RF transmissionlines 104, 106 so it will expand or contract when the RF transmissionsare extracted or inserted respectively. Environmental pump 1412 isconnected to flexible hydrocarbon barrier 1410 to capture all oil andgas that passes around center conductor RF transmission lines 104, 106in the main sealing surface.

Center conductor RF transmission lines 104, 106 can be movedindividually or both at once. As center conductor RF transmission lines104, 106 are first inserted it may be desirable to move themindividually so the end points of each, which are attached to one ofmany forms of RF couplers 202, 204 discussed, can be accurately placedin the production portion of the well for RF application. After theinitial insertion, center conductor RF transmission lines 104, 106 maybe moved simultaneously to ensure they stay at the same relativeposition within hydrocarbon bearing strata 126. Moving center conductorRF transmission lines 104, 106 simultaneously also reduces the time toperform the operation.

As designed, no oil or gas will escape during repositioning of centerconductor RF transmission lines 104, 106. However, as an extraprecaution, a flame extinguishing system will be used to prevent theauto ignition of hydrocarbons that are above the flashpoint temperaturein air. This system will be always on and has temperature sensors forauto deployment of flame extinguishing chemicals. The system will alsohave manual controls so that it can be activated if needed.

The open ends of center conductor RF transmission lines 104, 106 arenever exposed to product flow. Product flow only occurs around thelocation of the joint when center conductor RF transmission line 104,106 joint has been made and sealed. The flow of product is neverinterrupted. An adapter to connect center conductor RF transmission line104, 106 to a lift crane is necessary and will be a smaller version ofadapters already in use for well pipe. It will differ in that it willallow the lowering and retracting of two pipes at one time.

Returning to FIG. 1, dry fracture shale energy extraction system 100system will have central control, which will monitor down holeconditions and make adjustments as necessary to optimize the process.The sensors for this system are described in more detail with referenceto FIG. 15.

FIG. 15 illustrates example sensor suite 1500, which will regulate andoptimize the functioning of dry fracture shale energy extraction system100 in accordance with aspects of the present invention.

As shown in the figure, sensor suite 1500 includes pressure temperatureand flow sensor suites 1502, VSWR meters 1504, and a mini quake seismicarray 1506.

Pressure, temperature, and flow sensor suites 1502 are attached to thewell pipe at various points along the oil and gas producing portion ofthe well and at hydrocarbon lock 108. One pressure, temperature, andflow sensor suite 1502 is also attached to the input to oil storage tank118. VSWR meters 1504 are attached to both primary-phase centerconductor RF transmission line 104 and secondary-phase center conductorRF transmission line 106. Mini quake seismic sensor 1506 is attached tothe ground above the oil producing parts of the well.

Pressure temperature, and flow sensor suites 1502 may be any device orsystem, which measure system parameters to allow optimized operation.VSWR meters 1504 may be any device or system, which measure RF energyreflecting back up the RF transmission lines. Mini quake seismic array1506 may be any device or system, which measures crack activity ashydrocarbon bearing strata 126 heats.

In operation, sensor suite 1500 will optimize the heating processsorting between various priorities such as maximizing cracking,maximizing in situ retorting, and keeping cracks open. This will involvethe use of models, which use known system parameters along with sensorinputs to feed algorithms, which decide which of the control parametersto adjust in a given time interval. It will measure pressure,temperature, flow, and cracking to determine when it is necessary tochange the energy application point and alert the operator. By assessingthe product flow and heating history it will determine when additionalheating is necessary to reopen cracks that are starting to seal and/orcause new cracks in a previously heated block of hydrocarbon bearingstrata 126. Controllable parameters are: magnitude, phase, and frequencyof the RF energy, location of RF couplers 202, 204.

Returning to FIG. 1, the heating process for dry fracture shale energyextraction system will now be discussed in more detail. The heatingprocess consists of energizing the set of underground three-dimensionalunderground electromagnetic arrays sequentially. The particular heatingprocess described herein is for the case of an n by m three-dimensionalunderground electromagnetic array of well bores being energized in an nby 2 groups. Other groupings are possible.

Starting at the three-dimensional underground electromagnetic array inthe horizontal portion of the well closest to vertical well pipe section114, RF energy will be applied to the three-dimensional undergroundelectromagnetic array over a period of months (1 to 15). The length oftime is determined by power level, frequency, and size of the block ofhydrocarbon bearing strata 126 being heated. The process may start atthe end of the horizontal section adjacent to vertical well pipe section114 or at the horizontal end far from vertical well pipe section 114.The procedure is the same for either. It should also be noted that theprocess works for vertical sets of wells also. After the multi-monthperiod when hydrocarbon bearing strata 126 has been heated to ˜350°Celsius, the RF application point will be moved into the horizontallocation of the next three-dimensional underground electromagnetic arrayalong the well and the process started over again.

To account for changing conditions down the well hole, a feedbackcontroller will monitor the amount of RF power coming back up centerconductor RF transmission lines 104, 106 and will adjust the coupling ofcenter conductor RF transmission lines 104, 106 to RF couplers 202, 204and hence to the three-dimensional underground electromagnetic array tomaximize the flow of energy into the three-dimensional undergroundelectromagnetic array. As the amount of energy reflected back, upthrough center conductor RF transmission lines 104, 106 increases, theamount of capacitance or inductance in the down-hole matching sectionwill be adjusted. This adjustment will reduce the amount of energyreflected back, up through center conductor RF transmission lines 104,106. All adjustments required to keep energy backflow to a minimum willbe automated with reports of adjustments sent back to the operator. Thefeedback controller will alert the operator when the adjustments causethe system to approach its maximum range of tune ability.

The timing and location of the application of RF is also controlled byfeedback from the temperature and flow sensors. If a particular leg ofthe three-dimensional underground electromagnetic array is showingexcessive heat, then power may be reduced or eliminated from that leg ofthe three-dimensional underground electromagnetic array. The powerallocation between legs of the three-dimensional undergroundelectromagnetic array would then be adjusted to maximize desired heatingeffects. If flow measurements show that flow is reducing earlier thanpredicted, then additional heat may be applied to re-stimulate asnecessary. Pressure is also monitored to ensure down-hole conditions areconducive to flow into the well bore from hydrocarbon bearing strata 126and that the product has good support for flowing up the pipe to thewell head.

During the multi-month period of heating, the polarities of RFgenerators 102 may be changed to heat different portions of hydrocarbonbearing strata 126 at different times. This is described in more detailFIG. 16.

FIG. 16 illustrates heating patterns 1600, for a square,three-dimensional underground electromagnetic array realization of dryfracture shale energy extraction system 100, for heating specificsections of hydrocarbon bearing strata 126 by controlling which wellpipe segments contain primary-phase RF signals and which containsecondary-phase of two RF signals, in accordance with aspects of thepresent invention.

As shown in the figure, heating patterns 1600 for a square,three-dimensional underground electromagnetic array include a diagonalpattern 1602, a horizontal pattern 1604, and a vertical pattern 1606.

Heating patterns 1602, 1604, and 1606 all preferentially heat differentvolumes of hydrocarbon bearing strata 126.

By applying heat to precise locations, the stress can be adjusted tocause cracks to form in the desired locations to facilitate the flow ofoil and gas to the well. The growth of the crack field is measured bythe mini seismic array 1506 at surface of the earth 122 above the wellbore. This sensor can locate all new cracks above a certain size inthree-dimensional space as they form. If a certain volume is not gettingsufficient cracking, then the heat will be adjusted to cause thecracking to occur preferentially in that volume.

The expansion of water and, if shallow enough, the conversion of waterto steam, will both cause additional stresses and cracking. Further theconversion process of the solid kerogen to oil, gas and char results inadditional stress and subsequent cracking. Cracks from all thesecracking mechanisms will be measured and controlled to increase thepermeability of hydrocarbon bearing strata 126 and let the oil and gasflow to the horizontal well pipes for extraction.

The process will repeat for each three-dimensional undergroundelectromagnetic array along the well bore. During that time previouslyheated hydrocarbon bearing strata 126 will be producing oil and gas. Toensure that the maximum amount of oil and gas are harvested, hydrocarbonbearing strata 126 may be reheated to stimulate additional productoutput. The additional heat will cause additional cracking and reopenold cracks. Exact frequency and timing of reheating is dependent on theproperties of hydrocarbon bearing strata 126 and may be different foreach formation. The duration of reheating will be determined bymeasuring the flow rate, pressure and temperature at eachthree-dimensional underground electromagnetic array so that the amountof product coming out of any one of the three-dimensional undergroundelectromagnetic array volumes can be calculated. As soon as the amountof product coming from that three-dimensional undergroundelectromagnetic array is back to predicted levels, than the RFapplication point can be moved again.

It is obvious that the heating process is not confined to the volumeenclosed by the well bores. In fact the heated zone expands out aroundthe first set of well bores into volumes that are inside other sets ofwell bores. This is important since large volumes of hydrocarbon bearingstrata 126 are exposed to up to four or more heating and cooling cycles.The more heating and cooling cycles, the more dense the crack structureand the higher the permeability. These cracking cycles are measured viamini seismic sensor array 1506 at ground level.

In a well with a 5000 ft horizontal section, the overall heating processmay take up to 20 years. During this time, new producing zones are beingstimulated and older zones are producing. The period of time each zoneproduces will be determined by the initial heating, the refresh heatingrate and the rate of plastic deformation, which will be acting to closethe cracks. One measurement of crack closure is reduction of productflow. This will be closely monitored and additional RF stimulationapplied as necessary.

There are many methods in use or that have been proposed for theenhanced extraction of oil and gas from low permeability strata. Themost widely used is hydraulic fracturing, which was discussed above andhas the drawback of requiring large amounts of water. Problems existboth with obtaining the water and with disposing of the water. Obtainingthe water can lead to severe reduction in local aquifer levels orrequire the use of 400 to 500 tanker trucks that can damage rural roadssince most of these roads have not been designed to accommodate theheavy loading from the water trucks. Disposing of waste water is also aproblem since 10% to 50% of the millions of gallons of water pumped intothe ground returns to the surface. This returned water is contaminatedboth by heavy metals and by hydraulic fracturing fluids and must beeither cleaned up or disposed of in an environmentally friendly way.

Strip mining followed by surface pyrolysis has been used for many yearsas a method for extracting oil and gas from immature hydrocarbon bearingstrata. The main problem with strip mining are the massive amounts ofoverburden that must be removed to get to the hydrocarbon bearingstrata. Unless the hydrocarbon bearing strata is near the surface it isfrequently uneconomical to strip all the way down to the strata. Alsothere is much environmental resistance to the large amount of surfacedisruption associated with strip mining.

Other methods of enhanced extraction that have been proposed use heat,which emanates from the well pipe into the hydrocarbon bearing strata.This includes such techniques as steam heating or heaters inserted intothe well bores. The heat from these sources dissipates slowly into thehydrocarbon strata due to the low thermal conductivity of the strata.Thermal conductivity values range from approximately 0.5 W/(m*K). to 3W/(m*K). Great care must be taken to prevent overheating and melting ofthe heater and the rock near the well pipe. To make such systems work ittakes a slow enough heating rate to prevent overheating, which means itcan take years to heat even small volumes of shale.

RF based systems have been proposed using antennas. These systems havesimilar problems to well bore heating methods since the near fields ofthe antenna cause heating immediately adjacent to the well bore.Antennas, therefore, act like local heaters and have the same problemswith overheating as discussed above.

The system and method described herein is directed toward the use of RFenergy to enhance the extraction of oil and gas from hydrocarbon bearingstrata. It uses a three-dimensional underground electromagnetic array toguide RF energy to where the energy is deposited as heat into thehydrocarbon bearing strata. The three-dimensional undergroundelectromagnetic array is a guided wave structure, not an antennastructure, to minimize the unwanted effects of near fields associatedwith antennas. In one realization the legs of the three-dimensionalunderground electromagnetic array are comprised of production well pipe.

The system and method are designed to work along the entire extent of ahorizontally drilled well bore such as are used to efficiently extractoil and gas from hydrocarbon bearing strata with large horizontal extendand smaller vertical extent. There are multiple three-dimensionalunderground electromagnetic arrays along the length of the well bore soindividual volumes of rock (e.g. 100,000 tons, 50,000 cubic yards) maybe heated at one time.

The heat deposited in the hydrocarbon bearing strata has two effects.First it causes stresses in the hydrocarbon strata that will causecracking and will increase the permeability of the strata. This stressesare caused by thermal gradients and by differential thermal expansion.The stress required to cause cracking may also be reduced by chemicalchanges in the hydrocarbon strata, which reduce the strength of therock. Second it will cause in situ pyrolysis of the kerogen in thestrata releasing additional oil and gas to be recovered.

The release of the additional oil and gas combined with additional wellpipes required to form the arrays means that more oil and gas per volumewill be recovered than through any other method of enhanced oil and gasproduction. Further the system and method herein will not require thelarge amount of water that is currently used in hydraulic fracturing.

The system and method described herein has several benefits overprevious methods for extracting oil and gas from low permeability shaleand for performing in situ pyrolysis.

Firstly, the system does not use water to increase the permeability ofthe hydrocarbon bearing strata. There is no need for large volumes ofwater to be transported to the site or for the environmental cleanup ordisposal of large volumes of water coming back up the well pipe.

Secondly, the system uses electromagnetic guiding structures, not RFantennas. As noted above RF antennas have near fields, which causeunwanted preferential heating immediately adjacent to the wellbore.Electromagnetic guiding arrays do not have the same near field structureas antennas. In the case of electromagnetic guiding arrays the onlypreferential heating near the well bore is caused by geometry.

Thirdly, the RF energy is dispersed throughout the volume of the threedimensional underground electromagnetic array so the hydrocarbon stratais heated much more uniformly than simple well bore heaters. The heat isdeposited out in the hydrocarbon bearing strata and does not have to beconducted by low thermal conductivity rock to where it is needed tocause cracking and pyrolysis.

Fourthly, the system is designed to work in situ, the problemsassociated with strip mining are removed. There is minimal surfacedisruption and no cost associated with removing large amounts ofoverburden.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A system comprising: a first primary-phase wellpipe segment; a primary-phase dielectric spacer connected to said firstprimary-phase well pipe segment; a second primary-phase well pipesegment connected to said primary-phase dielectric spacer such that saidprimary-phase dielectric spacer is disposed between said firstprimary-phase well pipe segment and said second primary-phase well pipesegment; a first RF transmission line operable to be disposed into saidfirst primary-phase well pipe segment and into said second primary-phasewell pipe segment and operable to transmit a first RF signal; a first RFcoupler operable to be disposed within one of said first primary-phasewell pipe segment and said second primary-phase well pipe segment,operable to couple the first RF signal from said first RF transmissionline to said first primary-phase well pipe segment when disposed withinsaid first primary-phase well pipe segment and operable to couple thefirst RF signal from said first RF transmission line to said secondprimary-phase well pipe segment when disposed within said secondprimary-phase well pipe segment; a first secondary-phase well pipesegment; a secondary-phase dielectric spacer connected to said firstsecondary-phase well pipe segment; a second secondary-phase well pipesegment connected to said secondary phase dielectric spacer such thatsaid secondary-phase dielectric spacer is disposed between said firstsecondary-phase well pipe segment and said second secondary-phase wellpipe segment; a second RF transmission line operable to be disposed intosaid first secondary-phase well pipe segment and into said secondsecondary-phase well pipe segment and operable to transmit a second RFsignal; and a second RF coupler operable to be disposed within one ofsaid first secondary-phase well pipe segment and said secondsecondary-phase well pipe segment, operable to couple the second RFsignal from said second RF transmission line to said firstsecondary-phase well pipe segment when disposed within said firstsecondary-phase well pipe segment and operable to couple the second RFsignal from said second RF transmission line to said secondsecondary-phase well pipe segment when disposed within said secondsecondary-phase well pipe segment, wherein said first primary-phase wellpipe segment and said first secondary-phase well pipe segment form atwo-wire transmission line when said first RF coupler is disposed withinsaid fast primary-phase well pipe segment and when said second RFcoupler is disposed within said second secondary-phase well pipesegment.
 2. The system of claim 1, wherein said first RF transmissionline is operable to transmit the first RI signal having a primary-phaseas a function of time, wherein said second RF transmission line isoperable to transmit the second RF signal having a secondary-phase as afunction of time, and wherein the primary-phase is 180° out of phasewith respect to the secondary-phase.
 3. The system of claim 1, whereinsaid first primary-phase well pipe segment, said primary-phasedielectric spacer and said second primary-phase well pipe segment aredisposed along a first axis, wherein said first secondary-phase wellpipe segment, said secondary-phase dielectric spacer and said secondsecondary-phase well pipe segment are disposed along a second axis, andwherein the first axis and the second axis are parallel with oneanother.
 4. The system of claim 1, wherein said first RF coupler isoperable to couple the first RF signal from said first RF transmissionline to said first primary-phase well pipe segment via a directconnection.
 5. The system of claim 1, wherein said first RF coupler isoperable to inductively couple the first RF signal from said first RFtransmission line to said first primary-phase well pipe segment.
 6. Thesystem of claim 1, wherein said first RF coupler is operable tocapacitively couple the first RF signal from said first RF transmissionline to said first primary-phase well pipe segment.
 7. The system ofclaim 1, wherein said first primary-phase well pipe segment is separatedfrom said first secondary-phase well pipe segment by a separationvolume, and wherein said first RF coupler is operable to couple thefirst RF signal from said first RF transmission line to said firstprimary-phase well pipe segment when said first RF transmission line isdisposed within said first primary-phase well pipe segment and saidsecond RF coupler is operable to couple the second RF signal from saidsecond RF transmission line to said first secondary-phase well pipesegment when said second RF transmission line is disposed within saidfirst secondary-phase well pipe segment so as to heat the separationvolume.
 8. The system of claim 1, further comprising an RF signalgenerator operable to provide the first RF signal to said first RFtransmission line and to provide the second RF signal to said second RFtransmission line.
 9. A method comprising: providing a first well pipeincluding a first primary-phase well pipe segment, a primary-phasedielectric spacer, a second primary-phase well pipe segment, a first RFtransmission line and a first RF coupler, the primary-phase dielectricspacer being connected to the first primary-phase well pipe segment, thesecond primary-phase well pipe segment being connected to theprimary-phase dielectric spacer such that the primary-phase dielectricspacer is disposed between the first primary-phase well pipe segment andthe second primary-phase well pipe segment, the first RF transmissionline being operable to be disposed into the first primary-phase wellpipe segment and into the second primary-phase well pipe segment andbeing operable to transmit a first RF signal and the first RF couplerbeing operable to be disposed within one of the first primary-phase wellpipe segment and the second primary-phase well pipe segment, beingoperable to couple the first RF signal from the first RF transmissionline to the first primary-phase well pipe segment when disposed withinthe first primary-phase well pipe segment and being operable to couplethe first RF signal from the first RF transmission line to the secondprimary-phase well pipe segment when disposed within the secondprimary-phase well pipe segment; providing a second well pipe includinga first secondary-phase well pipe segment, a secondary-phase dielectricspacer, a second secondary-phase well pipe segment, a second RFtransmission line and a second RF coupler, the secondary-phasedielectric spacer being connected to the first secondary-phase well pipesegment, the second secondary-phase well pipe segment being connected tothe secondary-phase dielectric spacer such that the secondary-phasedielectric spacer is disposed between the first secondary-phase wellpipe segment and the second secondary-phase well pipe segment, thesecond RF transmission line being operable to be disposed into the firstsecondary-phase well pipe segment and into the second secondary-phasewell pipe segment and being operable to transmit a second RF signal andthe second RF coupler being operable to be disposed within one of thefirst secondary-phase well pipe segment and the second secondary-phasewell pipe segment, the second RF coupler being operable to couple thesecond RF signal from the second RF transmission line to the firstsecondary-phase well pipe segment when disposed within the firstsecondary-phase well pipe segment and the second RF coupler beingoperable to couple the second RF signal from the second RF transmissionline to the second secondary-phase well pipe segment when providing thefirst RF signal to the first RF transmission line to provide the firstRF signal to the first RF coupler to provide the first RF signal to thefirst primary-phase well pipe segment when disposed within the firstprimary-phase well pipe segment; and providing the second RF signal tothe second RF transmission line to provide the second RF signal to thesecond RF coupler to provide the second RF signal to the firstsecondary-phase well pipe segment when disposed within the firstsecondary-phase well pipe segment.
 10. The method of claim 9, whereinsaid providing the first RF signal to the first RF transmission linecomprises providing the first RF signal as a first RF signal having aprimary-phase as a function of time, wherein said providing the secondRF signal to the second RF transmission line comprises providing thesecond RF signal as a second RF signal having a secondary-phase as afunction of time, wherein the first RF transmission line is operable totransmit the first RF signal having the primary-phase as a function oftime, wherein the second RF transmission line is operable to transmitthe second RF signal having the secondary-phase as a function of time,and wherein the primary-phase is 180° out of phase with respect to thesecondary-phase.
 11. The method of claim 9, wherein said providing afirst well pipe comprises providing the first primary-phase well pipesegment, the primary-phase dielectric spacer and the secondprimary-phase well pipe segment disposed along a first axis, whereinsaid providing the second well pipe comprises providing the firstsecondary-phase well pipe segment, the secondary-phase dielectric spacerand the second secondary-phase well pipe segment disposed along a secondaxis, and wherein the first axis and the second axis are parallel withone another.
 12. The method of claim 9, further comprising: disposingthe first RF transmission line within the first primary-phase well pipesegment, wherein the first RF coupler couples the first RF signal fromthe first RF transmission line to the first primary-phase well pipesegment via a direct connection.
 13. The method of claim 9, furthercomprising: disposing the first RF transmission line within the firstprimary-phase, well pipe segment, wherein the first RF couplerinductively couples the first RF signal from the first RF transmissionline to the first primary-phase well pipe segment.
 14. The method ofclaim 9, further comprising: disposing the first RF transmission linewithin the first primary-phase well pipe segment, wherein the first RFcoupler capacitively couples the first RF signal from the first RFtransmission line to the first primary-phase well pipe segment.
 15. Themethod of claim 9, further comprising: disposing the first RFtransmission line within the first primary-phase well pipe segment; anddisposing the second RF transmission line within the firstsecondary-phase well pipe segment, wherein said providing the secondwell pipe comprises providing the second well pipe such that the firstprimary-phase well pipe segment is separated from the firstsecondary-phase well pipe segment by a separation volume, and whereinthe first RF coupler couples the first RF signal from the first RFtransmission line to the first primary-phase well pipe segment and thesecond RF coupler couples the second RF signal from the second RFtransmission line to the first secondary-phase well pipe segment so asto heat the separation volume.
 16. The method of claim 9, wherein saidproviding the first RF signal to the first RF transmission linecomprises providing the first RF signal via an RF signal generator. 17.A system comprising: an RF-transparent primary-phase well pipe operableto be disposed along a first axis; a first RF transmission line operableto be disposed into said RF-transparent primary-phase well pipe parallelto the first axis and operable to transmit a first RF signal; a firstdifferential line; an RF-transparent secondary-phase well pipe operableto be disposed along a second axis; a second RF transmission lineoperable to be disposed into said RF-transparent secondary-phase wellpipe parallel to the second axis and operable to transmit a second RFsignal; and a second differential line, wherein said first differentialline and said second differential line form a differential pair, whereinsaid first differential line is operable to be disposed within saidRF-transparent primary-phase well pipe at a first position along thefirst axis, is operable to be disposed within said RF-transparentprimary-phase well pipe at a second position along the first axis and isoperable to couple the first RF signal from said first RF transmissionline at the first position to said second differential line, and whereinsaid second differential line is operable to be disposed within saidRF-transparent secondary-phase well pipe at a first position along thesecond axis, is operable to be disposed within said RF-transparentsecondary-phase well pipe at a second position along the second axis andis operable to couple the second RF signal from said second RFtransmission line at the first position to said first differential line.18. The system of claim 17, wherein said RF-transparent primary-phasewell pipe is separated from said RF-transparent secondary-phase wellpipe by a separation volume, and wherein said first differential line isoperable to couple the first RF signal from said first RF transmissionline to said second differential line when said first RF transmissionline is disposed within said RF-transparent primary-phase well pipe andsaid second differential line is operable to couple the second RF signalfrom said second RF transmission line to said first differential linewhen said second RF transmission line is disposed within saidRF-transparent secondary-phase well pipe so as to heat the separationvolume.
 19. A method comprising: disposing an RF-transparentprimary-phase well pipe operable along a first axis; disposing a firstRF transmission line within the RF-transparent primary-phase well pipeparallel to the first axis; disposing a first differential line withinthe RF-transparent primary-phase well pipe; disposing an RF-transparentsecondary-phase well pipe along a second axis; disposing a second RFtransmission line within said RF-transparent secondary-phase well pipeparallel to the second axis; disposing a second differential line withinthe RF-transparent secondary-phase well pipe, providing a first RFsignal to the first RF transmission line to provide the first RF signalto the first differential line to provide the first RF signal TO thesecond differential line; and providing a second RF signal to the secondRF transmission line to provide the second RF signal to the differentialline to provide the second RF signal to the first differential line. 20.The method of claim 19, wherein said disposing an RF-transparentsecondary-phase well pipe along a second axis comprises separating theRF-transparent secondary-phase well pipe from the RF-transparentprimary-phase well pipe by a separation volume, and wherein saidproviding a second RF signal to the second RF transmission linecomprises providing a second RF signal to the second RF transmissionline so as to heat the separation volume.